Researchers found that zebrafishes can sense water motion the same way humans can.In the new study, they discovered a gene called tmc2b in zebrafish which also found in humans that convert water motion into electrical impulses.
Zebrafish or Danio rerio is a tropical fish of the minnow family commonly used for scientific research and kept in aquariums.Zebrafishes have no economic importance to commercial fisheries as a food source, but are popular in fish trade for aquaria.Geneticists use zebrafishes as a common model organism in various research, such as studies of vertebrate development and gene function, an alternative to rats and mice models.
One of the most interesting studies conducted in zebrafishes is regeneration.They can regenerate many parts of their body, such as fins, skin, heart, and brain.Researchers usual amputate the dorsal and ventral tail fins of zebrafishes then analyze regeneration for any mutation.Australian scientists published a study in 2011 unveiling a special protein called the fibroblast growth factor.The special protein prevented glial scarring in healed spinal cords.
In the latest study, the tmc2b gene allows zebrafishes to detect the direction of water flow.In humans, it helps hair cells inside the ears to detect various ranges of sounds.However, mutations in the tmc2b gene can cause deafness in humans.The hair cells located in bodies of zebrafishes face different directions to detect water motion.But the researchers found in the new study that hair cells use the tmc2b gene a little differently.
Dr.McDermott and Dr.Ruben Stepanyan, an assistant professor of otolaryngology at CaseMed, delved into mechanotransduction.They discovered that hair cells on the zebrafishes use the deafness gene based on their orientation.Hair cells facing the front helps with forward swimming, but hair cells at back can sense pursuers.
"We found detection of water flow from the front of the fish is more dependent on the zebrafish gene tmc2b than water flow from the back of the fish.Water flowing from the front of the fish accompanies forward swimming, therefore, it is routine.But water coming from the rear could mean a predator in pursuit.Zebrafish, therefore, use different molecular mechanisms to distinguish water flow direction," said Dr.McDermott Jr, an associate professor of otolaryngology at the Case Western Reserve University School of Medicine.
Mechanotransduction is a mechanism on how cells detect physical forces and convert them to biological responses.This mechanism is a form of sensory transduction, responsible for many physiological senses such as balance, hearing, and touch.The physical forces are converted to either chemical or electrical signals transmitted to sensory neurons to reach the brain.There are about 3,500 inner hair cells and 12,000 outer hair cells found in the human cochlea, which can detect sound and head motion to process hearing and balance control.
Using their findings, the researchers created a mechanosensory map of the hair cells in zebrafish.The map contains important aspects about the hair cells, such as:
- The relationship between the hair cell's location and orientation to sense the motion of water.
- The independence and dependence of different hair cells on the deafness gene in order to function.
"Our findings suggest that in mammals, including humans, there may be molecular differences between hair cells that allow us to hear the wonderful range of sounds that we enjoy," said Dr.McDermott.
The human ear has an audible frequency range of 20 Hz to 20 kHz, capable of detecting pressure variations of less than one billionth of atmospheric pressure.The structures of the outer and middle ear enhance the sensitivity of the ear.But the incredible function of the organ can be severed by various health conditions, such as ear infections, meningitis, measles, and chicken pox.
Otitis media is the inflammation of the middle ear which usually caused by fluid buildup.It is the most commonly diagnosed diseases in infants and young children, with a prevalence rate of 75 percent of children experiencing at least one episode by their third birthday.Symptoms of otitis media include inattentiveness, unexplained irritability, frequent pulling or scratching of the ears, and increasing the loudness of TV sets and radio units.
About two to three in every 1,000 children are born with a detectable level of hearing loss in one or both ears in the United States, while more than 90 percent of deaf children are born to parents with normal hearing ability.Hearing loss can lead to many complications and most people who are deaf suffer wwith some psychological, physical, and social issues.
In children, hearing loss can delay the development of their language and speech skills.The deficit in speech can lead to learning problems and poor academic performance, while the deficit in communication skills can lead to social isolation.Specifically, children with hearing loss face challenges in vocabulary, sentence construction, verbal conversation, and socialization, according to the American Speech-Language-Hearing Association.